[Bret L]

The concept is well proven although there is no reasonably priced one
available at this time. In quantity it could be inexpensive yet,
superior to all other carts which are commercially available today.
Alas, without a semiconductor fab it's beyond DIY efforts.

It's ironic also to note that of the really expensive carts today,
the majority are actually quite colored and not particularly accurate.
The most accurate measured performance tends to come from moderately
priced carts.